WIND TURBINE ROTOR BALANCING METHOD, ASSOCIATED SYSTEM AND WIND TURBINE

Abstract

The present invention relates to a wind turbine rotor balancing method which compensates imbalances between the centres of gravity of the wind turbine blades, in both magnitude and position along said blades, so that the amount of mass needed to carry out this balancing method is minimized, while reducing the loads and vibrations associated with a position of the centre of gravity of the rotor not aligned with the axis of rotation thereof, wherein the invention further relates to the wind turbine rotor balancing system and the wind turbine balanced with the above method.

Claims

1. A wind turbine rotor balancing method, the wind turbine comprising a rotor which comprises at least two blades, the method comprising the following steps: a step of identifying a reference angular position for each of the at least two blades; a step of calculating a magnitude, m.sub.x, of rotor imbalance based on a mass, M.sub.iT, of each of the at least two blades with respect to a centre of the rotor; a step of calculating a phase, φ.sub.x, of rotor imbalance; and a balancing step, wherein the balancing step is carried out at least if the phase, φ.sub.x, of rotor imbalance lies outside a permissible angular range relative to the reference angular positions.

2. The method of claim 1 wherein the balancing step is carried out if at least one of the following conditions is additionally met: the difference between the masses of the at least two blades, difference calculated taking the blades two by two, |M.sub.iT−M.sub.jT|∀.sub.i,j being i≠j, is above a first threshold value; the magnitude of rotor imbalance, m.sub.x, is above a second threshold value.

3. The method of claim 1 wherein the balancing step is performed by placing at least one balancing mass in at least one of the at least two blades.

4. The method of claim 1 comprising, prior to the step of calculating a magnitude, m.sub.x, of rotor imbalance, a step of weighing each of the at least two blades to determine the mass of each one wherein the weighing step is carried out through at least two weighing points, preferably a first weighing point in the vicinity of a root of the blade and a second weighing point in the vicinity of a tip of the blade.

5. The method of claim 1 wherein the magnitude of rotor imbalance calculated in the step of calculating a magnitude of rotor imbalance is the resultant mass moment from the mass moments of each of the three blades relative to the centre of the rotor.

6. The method of claim 1 wherein the rotor comprises three blades, so that the step of identifying a reference angular position for each of the three blades is carried out with said reference angular positions for each of the blades being spaced 120° from each other.

7. The method of claim 4 wherein the step of weighing each of the at least two blades to determine the mass of each one is carried out through at least two weighing points, preferably a first weighing point in the vicinity of a root of the blade with which a root mass value, M.sub.ir, is obtained, and a second weighing point in the vicinity of a tip of the blade with which a tip mass value, M.sub.ip, is obtained so that the total mass of each of the blades is calculated as:
M.sub.iT=M.sub.ir+M.sub.ip

8. The method of claim 7 wherein the step of calculating a magnitude of rotor imbalance, said magnitude of rotor imbalance being the resultant mass moment from the mass moments of each of the three blades with respect to the centre of the rotor, comprises: a substep of calculating the centre of gravity of each blade relative to the root of each blade according to the following: ${\mathrm{CG}}_i=\frac{L_r.Math.M_{\mathrm{ir}}+L_p.Math.M_{\mathrm{ip}}}{M_{\mathrm{iT}}}.Math..Math.\mathrm{wherein}.Math..Math.i=1,2,3$ wherein L.sub.r is the distance between the first weighing point and the root of the blade and L.sub.P is the distance between the second weighing point and the root of the blade, and a substep of calculating the centre of gravity of each blade relative to the centre of the rotor according to the following: ${\left({\mathrm{CG}}_{\mathrm{rotor}}\right)}_i=\frac{\left(\mathrm{RC}+L_r\right).Math.M_{\mathrm{ir}}+\left(\mathrm{RC}+L_p\right).Math.M_{\mathrm{ip}}}{M_{\mathrm{iT}}}=\mathrm{RC}+{\mathrm{CG}}_i.Math..Math.\mathrm{wherein}.Math..Math.i=1,2,3$ wherein RC is the radius of the hub, and wherein the resultant mass moment from the mass moments of each of the three blades relative to the centre of the rotor is calculated as: $m_x=\sqrt{\begin{array}{c}{\left\{{M_{1.Math.T}\left({\mathrm{CG}}_{\mathrm{rotor}}\right)}_1-\frac{{M_{2.Math.T}\left({\mathrm{CG}}_{\mathrm{rotor}}\right)}_2+{M_{3.Math.T}\left({\mathrm{CG}}_{\mathrm{rotor}}\right)}_3}{2}\right\}}^2+\\ {\left\{\frac{\sqrt{3}}{2}.Math.\left({M_{2.Math.T}\left({\mathrm{CG}}_{\mathrm{rotor}}\right)}_2-{M_{3.Math.T}\left({\mathrm{CG}}_{\mathrm{rotor}}\right)}_3\right)\right\}}^2\end{array}}$

9. The method of claim 8 wherein the step of calculating a phase, φ.sub.x, of rotor imbalance is calculated as: ${\varphi }_x=\mathrm{atan}\left[\frac{{M_{1.Math.T}\left({\mathrm{CG}}_{\mathrm{rotor}}\right)}_1-\frac{{M_{2.Math.T}\left({\mathrm{CG}}_{\mathrm{rotor}}\right)}_2+{M_{3.Math.T}\left({\mathrm{CG}}_{\mathrm{rotor}}\right)}_3}{2}}{\frac{\sqrt{3}}{2}.Math.\left({M_{2.Math.T}\left({\mathrm{CG}}_{\mathrm{rotor}}\right)}_2-{M_{3.Math.T}\left({\mathrm{CG}}_{\mathrm{rotor}}\right)}_3\right)}\right]$

10. The Method according of claim 1 wherein the permissible angular range relative to the reference angular positions is ±45°, preferably ±30°.

11. A wind turbine rotor balancing system, the wind turbine comprising a set of components including a rotor which comprises at least two blades, wherein the system comprises: means for identifying a reference angular position for each of the at least two blades; first means for calculating a magnitude, m.sub.x, of rotor imbalance based on a mass, M.sub.iT, of each of the at least two blades with respect to a centre of the rotor; second means for calculating a phase, φ.sub.x, of rotor imbalance; and balancing means, wherein said balancing means are configured to act at least if the phase, φ.sub.x, of rotor imbalance lies outside a permissible angular range relative to the reference angular positions.

12. The system of claim 11 wherein the balancing means are configured to act, if at least one of the following conditions is met: the difference between the masses of the three blades, difference calculated taking the blades two by two, |M.sub.iT−M.sub.jT|∀.sub.i,j being i≠j is above a first threshold value, the magnitude, m.sub.x, of rotor imbalance is above a second threshold value.

13. The system of claim 11 wherein the balancing means are configured to place at least one balancing mass on at least one of the at least two blades.

14. The system of claim 11 further comprising weighing means for each of the three blades to determine the mass of each one, the weighing means comprise at least two weighing points, preferably a first weighing point placeable in the vicinity of the root of the blade and a second weighing point placeable in the vicinity of the tip of the blade.

15. A wind turbine balanced by a balancing method comprising the following steps: a step of identifying a reference angular position for each of the at least two blades; a step of calculating a magnitude, m.sub.x, of rotor imbalance based on a mass, M.sub.iT, of each of the at least two blades with respect to a centre of the rotor; a step of calculating a phase, φ.sub.x, of rotor imbalance; and a balancing step, wherein the balancing step is carried out at least if the phase, φ.sub.x, of rotor imbalance lies outside a permissible angular range relative to the reference angular positions; wherein the wind turbine comprises a rotor which comprises the at least two blades, wherein each of the at least two blades comprises the mass, M.sub.iT, wherein the rotor comprises the calculable magnitude, m.sub.x, of rotor imbalance and phase, φ.sub.x, of rotor imbalance, wherein the phase, φ.sub.x, of rotor imbalance is within the permissible angular range relative to at least one longitudinal direction of one of the at least two blades.

16. The wind turbine of claim 15 wherein the difference between the masses of the at least two blades, difference calculated taking the blades two by two, |M.sub.iT−M.sub.jT|∀.sub.i,j being i≠j is above a first threshold value.

17. The wind turbine of claim 15 wherein the magnitude, m.sub.x, of rotor imbalance is above a second threshold value.

18. The wind turbine of claim 15 wherein at least one of the at least two blades comprises at least one balancing mass.

19. The system of claim 12 wherein the balancing means are configured to place at least one balancing mass on at least one of the at least two blades.

20. The wind turbine of claim 16 wherein the magnitude, m.sub.x, of rotor imbalance is above a second threshold value.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0047] FIG. 1 shows a diagram of the step of identification of each of the three blades of the wind turbine rotor balancing method of the present invention according to the first preferred embodiment.

[0048] FIG. 2 shows a diagram of the step of weighing of each three blades of the first embodiment to determine the mass of each one of the wind turbine rotor balancing method of the present invention.

[0049] FIG. 3 shows a wind turbine balanced by the wind turbine rotor balancing method of the first embodiment of the present invention.

PREFERRED EMBODIMENT OF THE INVENTION

[0050] In a first preferred embodiment of the invention, the wind turbine rotor balancing method, the wind turbine comprising a rotor (1) which comprises three blades (2) arranged on a hub (8), comprises the following steps: [0051] a step of identifying a reference angular position for each of the three blades (2), said reference angular positions for each of the blades being spaced 120° from each other, as shown in FIG. 1, the blades being referenced as P1, P2 and P3; [0052] a step of weighing each of the three blades (2) to determine the mass of each one (2); [0053] a step of calculating a magnitude of rotor imbalance, which in this preferred embodiment is the resultant mass moment (m.sub.x) from the mass moments of each of the three blades (2) with respect to a centre (7) of the rotor (1); [0054] a step of calculating a phase of rotor imbalance (1); and [0055] a balancing step, wherein the balancing step is performed at least if the phase of rotor imbalance (1) lies outside a permissible angular range relative to the reference angular positions.

[0056] In this embodiment, the step of identifying a reference angular position for each of the three blades (2), comprises the following substeps: [0057] a substep of enumeration of each of the blades (2), for example with numbers 1, 2 and 3. [0058] a substep of labelling of each of the blades (2) with a number corresponding to the preceding enumeration substep.

[0059] In this embodiment, the step of weighing each of the three blades (2) to determine the mass of each one (2) is carried out through two weighing points, preferably a first weighing point (3) in the vicinity of a root (4) of the blade (2) whereby a root mass value (M.sub.ir) is obtained and a second weighing point (5) in the vicinity of a tip (6) of the blade (2) whereby a tip mass value (M.sub.ip) is obtained, so that the total mass of each of the blades (2) is calculated as:

M.sub.iT=M.sub.ir+M.sub.ip wherein i=1,2,3

[0060] In this embodiment, the step of calculating a magnitude of rotor imbalance, said magnitude of rotor imbalance being the resultant mass moment (m.sub.x) from the mass moments of each of the three blades (2) relative to the centre (7) of the rotor (1), comprises: [0061] A substep of calculating the centre of gravity of each blade (2) relative to the root (4) of each blade (2) according to the following:

[00001]${\mathrm{CG}}_i=\frac{L_r.Math.M_{\mathrm{ir}}+L_p.Math.M_{\mathrm{ip}}}{M_{\mathrm{iT}}}.Math..Math.\mathrm{wherein}.Math..Math.i=1,2,3$

[0062] wherein L.sub.r is the distance between the first weighing point (3) and the root (4) of the blade (2) and L.sub.P is the distance between the second weighing point (5) and the root (4) of the blade (2), and [0063] a substep of calculating the centre of gravity of each blade (2) relative to the centre (7) of the rotor (1) according to the following:

[00002]${\left({\mathrm{CG}}_{\mathrm{rotor}}\right)}_i=\frac{\left(\mathrm{RC}+L_r\right).Math.M_{\mathrm{ir}}+\left(\mathrm{RC}+L_p\right).Math.M_{\mathrm{ip}}}{M_{\mathrm{iT}}}=\mathrm{RC}+{\mathrm{CG}}_i.Math..Math.\mathrm{wherein}.Math..Math.i=1,2,3$

[0064] wherein RC is the radius of the hub (8), and

[0065] wherein the resultant mass moment (m.sub.x) from the mass moments of each of the three blades (2) relative to the centre (7) of the rotor (1) is calculated as:

[00003]$m_x=\sqrt{\begin{array}{c}{\left\{{M_{1.Math.T}\left({\mathrm{CG}}_{\mathrm{rotor}}\right)}_1-\frac{{M_{2.Math.T}\left({\mathrm{CG}}_{\mathrm{rotor}}\right)}_2+{M_{3.Math.T}\left({\mathrm{CG}}_{\mathrm{rotor}}\right)}_3}{2}\right\}}^2+\\ {\left\{\frac{\sqrt{3}}{2}.Math.\left({M_{2.Math.T}\left({\mathrm{CG}}_{\mathrm{rotor}}\right)}_2-{M_{3.Math.T}\left({\mathrm{CG}}_{\mathrm{rotor}}\right)}_3\right)\right\}}^2\end{array}}$

[0066] In this embodiment, the step of calculating a phase (φ.sub.x) of rotor imbalance is calculated as:

[00004]${\varphi }_x=\mathrm{atan}\left[\frac{{M_{1.Math.T}\left({\mathrm{CG}}_{\mathrm{rotor}}\right)}_1-\frac{{M_{2.Math.T}\left({\mathrm{CG}}_{\mathrm{rotor}}\right)}_2+{M_{3.Math.T}\left({\mathrm{CG}}_{\mathrm{rotor}}\right)}_3}{2}}{\frac{\sqrt{3}}{2}.Math.\left({M_{2.Math.T}\left({\mathrm{CG}}_{\mathrm{rotor}}\right)}_2-{M_{3.Math.T}\left({\mathrm{CG}}_{\mathrm{rotor}}\right)}_3\right)}\right]$

[0067] In this embodiment, the permissible angular range relative to the reference angular positions of the balancing step, is one of the following:

65°≦φ.sub.x≦115°

185°≦φ.sub.x≦235°

305°≦φ.sub.x≦355°,

[0068] the reference angular positions being 90°, 210° and 330° respectively.

[0069] In a second embodiment, the balancing step is carried out, if in addition to the phase of rotor imbalance lying outside a permissible angular range relative to the reference angular positions, at least the following is fulfilled: the difference between the masses of the three blades (2), difference calculated taking the blades (2) two by two, is above a first threshold value with respect to a nominal mass (M.sub.n) of the blades (2), wherein the first threshold value is less than 2%, i.e.

[00005]$\frac{\left|M_{\mathrm{iT}}-M_{\mathrm{jT}}\right|}{M_n}.Math.100<2.Math.\%.Math..Math.{\forall }_{i,j.Math..Math.\mathrm{being}.Math..Math.i\ne j}$

[0070] In a third embodiment, the allowable angular range relative to the reference angular positions is ±45°, preferably ±30°. That is, the permissible angular range is 90° centred on the reference positions, with 45° in both directions around the reference positions, preferably, the permissible angular range is 60° centred on the reference positions, with 30° in both directions around the reference positions. FIG. 3 shows a wind turbine balanced by the wind turbine rotor balancing method according to this third embodiment, wherein the permissible angular range relative to the reference angular positions is ±30°.

[0071] The wind turbine rotor balancing system can implement the method described in the first and second examples of preferred embodiment, while the wind turbine balanced by the wind turbine rotor balancing method described in the first and second embodiments, comprises a set of components including a rotor (1) which comprises three blades (2) wherein the blades (2) are spaced 120° from each other and each of the blades (2) comprises a mass defined as M.sub.iT=M.sub.ir+M.sub.ip wherein i=1, 2, 3 wherein the rotor (1) comprises: [0072] a magnitude of rotor imbalance calculated based on the mass of each of the three blades (2) relative to the centre (7) of the rotor (1), said magnitude of rotor imbalance being the resultant mass moment (m.sub.x) from the mass moments of each of the three blades (2) relative to the centre (7) of the rotor (1) according to the expression

[00006]$m_x=\sqrt{\begin{array}{c}{\left\{{M_{1.Math.T}\left({\mathrm{CG}}_{\mathrm{rotor}}\right)}_1-\frac{{M_{2.Math.T}\left({\mathrm{CG}}_{\mathrm{rotor}}\right)}_2+{M_{3.Math.T}\left({\mathrm{CG}}_{\mathrm{rotor}}\right)}_3}{2}\right\}}^2+\\ {\left\{\frac{\sqrt{3}}{2}.Math.\left({M_{2.Math.T}\left({\mathrm{CG}}_{\mathrm{rotor}}\right)}_2-{M_{3.Math.T}\left({\mathrm{CG}}_{\mathrm{rotor}}\right)}_3\right)\right\}}^2\end{array}}$

and [0073] a phase (φ.sub.x) of rotor imbalance according to the expression

[00007]${\varphi }_x=\mathrm{atan}\left[\frac{{M_{1.Math.T}\left({\mathrm{CG}}_{\mathrm{rotor}}\right)}_1-\frac{{M_{2.Math.T}\left({\mathrm{CG}}_{\mathrm{rotor}}\right)}_2+{M_{3.Math.T}\left({\mathrm{CG}}_{\mathrm{rotor}}\right)}_3}{2}}{\frac{\sqrt{3}}{2}.Math.\left({M_{2.Math.T}\left({\mathrm{CG}}_{\mathrm{rotor}}\right)}_2-{M_{3.Math.T}\left({\mathrm{CG}}_{\mathrm{rotor}}\right)}_3\right)}\right]$

[0074] wherein the phase (φ.sub.x) of rotor imbalance is within a permissible angular range with respect to at least one longitudinal direction (11) of one of the three blades (2), said permissible angular range being ±45°, more preferably ±30°, and more preferably ±25°.

[0075] Additionally, the difference between the masses of the three blades (2), difference calculated taking the blades (2) two by two, is above a first threshold value, wherein the first threshold relative to a nominal mass (M.sub.n) of the blades (2) it is less than 2%, i.e.

[00008]$\frac{\left|M_{\mathrm{iT}}-M_{\mathrm{jT}}\right|}{M_n}.Math.100<2.Math.\%.Math..Math.{\forall }_{i,j.Math..Math.\mathrm{being}.Math..Math.i\ne j}$

[0076] The wind turbine further comprises a nacelle (9) and a tower (10).